The invention relates to a pilot burner for a device for burning off solid particles, in particular soot particles, in the exhaust gas of internal combustion engines of the type described further hereinafter.
Burnoff devices of this kind are used in particular in motor vehicles having Diesel engines, for the direct disposal of the soot filtered out of the exhaust gas by electrostatic soot traps. Along with a secondary flow of exhaust gas that amounts to less than 1% of the total exhaust gas, this soot is delivered to the combustion chamber of the burnoff device, where it is burned at a flame temperature between 550.degree. C. and 1000.degree. C. The combustion products free of toxic substances, and the remaining gases, are expelled via the engine exhaust system. To generate the burnoff flame, a pilot burner, as described for example in German Offenlegungsschrift No. 36 21 914, is mounted on the combustion chamber of the burnoff device. In this pilot burner, embodied as a swirl burner, liquid fuel and combustion air in metered amounts are swirled in the mixture preparation chamber, and the mixture is delivered via the mixture outlet opening to the combustion chamber, where after ignition it burns off, along with the soot-laden exhaust gas. The ignition is effected by a glow plug, by the ignition of the mixture on its incandescent coil. After ignition of the mixture has been ignited and heating of the glow element in the mixture preparation chamber, the glow element takes on the function of stabilizing the flame formation, so that the glow plug can be switched off again and is needed only for the startup or intermittent operation of the burnoff device. The structure of the pilot burner is definitive for the quality of the mixture preparation and for the load on the glow plugs; accommodating the glow plug in the separate receiving chamber keeps it out of range of the flame, which prevents it from being thermally overloaded.